A wireless mobile communications system evolves from a second generation (2G) communications system, for example, a GSM (Global System for Mobile Communication), and a third generation (3G) communications system, for example, a UMTS (Universal Mobile Telecommunications System) into a fourth generation (4G) communications system. The 4G communications system uses an LTE (Long Term Evolution) access technology, where an access network of the 4G communications system is referred to as an E-UTRAN (Evolved Universal Terrestrial Radio Access Network)
An LTE network is a packet switched (PS for short) network, and cannot provide a circuit switched (CS for short) service, and a circuit switched fallback (CSFB for short) is used as a solution to the circuit switched service in the LTE network. A main idea of the CSFB is that a terminal camps on the E-UTRAN, and when the terminal executes the circuit switched service, the terminal falls back from the LTE network to the 2G network or the 3G network, and the terminal completes the circuit switched service in the 2G network or the 3G network. A specific process is as follows.
When the terminal needs to initiate the circuit switched service, the terminal first falls back from the LTE network to the 2G network or the 3G network, and the terminal returns to the LTE network after completing the execution of the circuit switched service once. If the terminal continues to initiate the circuit switched service again, the terminal needs to fall back from the LTE network to the 2G network or the 3G network again, and the terminal returns to the LTE network again after completing the execution of the circuit switched service this time. If the terminal needs to initiate the circuit switched service multiple times within a preset time period, the terminal needs to execute an operation of falling back from the LTE network to the 2G network or the 3G network multiple times, and execute an operation of returning from the 2G network or the 3G network to the LTE network multiple times. Therefore, there are disadvantages that power consumption of the terminal is relatively large and a delay of the circuit switched service is relatively long.
In conclusion, currently, in a process of processing the circuit switched service by the terminal located in the LTE network, there are the disadvantages that the power consumption of the terminal is relatively large and the delay of the circuit switched service is relatively long.